“Nidal” is an honorific, the name bestowed upon the ruler of Circadia (and by extension the guardian of the Mana Chasm). Technically this person retains their full name, with the suffix “Nidal of Circadia” attached. Most simply just take their full name as “Nidal”.
Nidal during the War of Heroes
The Nidal during the War of Heroes was Nidal Finnoc, a warrior who served as a paladin of Helm in the battle against Finnoc. The details of his reign are unclear, though it is known that his reign was fairly peaceful save for the discontent with Heroes.
Nidal during the Dark War
The Nidal during the Dark War was one Carius Geoff, though he changed his last name to “Nidal” upon receiving the honor. In the final moments of the war, The Gladiators teleported into the heart of the city itself to the steps of the Great Clocktower. Meyas fought Carius in a duel, eventually besting him after a long and bloody battle.